You should still have "Open All in Tabs"; I can't think of any setting that would remove it.

Are you using any add-on(s) or optional userChrome.css file rule(s) that modify bookmarks in any way?

jscher2000, Only after Firefox updated (did twice???) did it lose the complete list of tabs in Folders; after closing and reboot opening Firefox again then the full list of tabs, i.e., Bookmarks, had returned. Problem was with missing tabs, not the "Open all in Tabs" option, which does appear depending on how fast I scroll. Thanks for quick help.

JJE

If you use Sync then best is to disconnect Sync temporarily during troubleshooting.

This can be caused by a problem with the places.sqlite and favicons.sqlite databases in the Firefox profile folder.

• use "Verify Integrity" button on the "Help -> Troubleshooting Information" (about:support) page

If errors are reported with "Verify Integrity", close and restart Firefox and retry.

If "Verify Integrity" cannot repair places.sqlite, rename/remove all places.sqlite and favicons.sqlite files in the Firefox profile folder. Firefox will rebuild places.sqlite and restore the bookmarks from a recent JSON backup in the bookmarkbackups folder.

• keep a backup copy of places.sqlite in case a new places.sqlite database has to be created

See also:

• https://support.mozilla.org/en-US/kb/Bookmarks+not+saved#w_fix-the-bookmarks-file
• https://support.mozilla.org/en-US/kb/fix-bookmarks-and-history-will-not-be-functional

You can use the button on the "Help -> Troubleshooting Information" (about:support) page to go to the current Firefox profile folder or use the about:profiles page.

• Help -> Troubleshooting Information -> Profile Folder/Directory:
  Windows: Open Folder; Linux: Open Directory; Mac: Show in Finder
• https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data